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Ian Campbell
fb31b1475f
pygrub (in identify_disk_image()) detects a DOS style partition table via the presence of the 0xaa55 signature at the end of the first sector of the disk. However this signature is also present in whole-disk configurations when there is an MBR on the disk. Many filesystems (e.g. ext[234]) include leading padding in their on disk format specifically to enable this. So if we think we have a DOS partition table but do not find any actual partition table entries we may as well try looking at it as a whole disk image. Worst case is we probe and find there isn't anything there. This was reported by Sjors Gielen in Debian bug #745419. The fix was inspired by a patch by Adi Kriegisch in https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=745419#27 Tested by genext2fs'ing my /boot into a new raw image (works) and then: dd if=/usr/lib/grub/i386-pc/g2ldr.mbr of=img conv=notrunc bs=512 count=1 to add an MBR (with 0xaa55 signature) to it, which after this patch also works. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Acked-by: Wei Liu <wei.liu2@citrix.com> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com> Cc: 745419-forwarded@bugs.debian.org